Neural Representations of Personally Familiar and Experimentally Familiar Faces Across Adulthood

Face recognition is thought to reflect complementary functions of two brain networks. A core system is thought to support perceptual processing of faces, whereas an extended system represents affective and biographical knowledge that supports familiarity-based discrimination. However, the representational format of face-evoked responses within structures comprising each system is not well understood. Here, we applied RSA to fMRI data to characterize the representational structure of personally familiar, experimentally familiar, and novel faces in younger and older adults. This approach revealed that perirhinal cortex (PRC), a node in the extended face processing system, represented personally familiar and experimentally familiar faces in distinct patterns of activity in young adults; personally familiar faces were repelled from one another, whereas experimentally familiar faces were drawn near one another. Corresponding results from PRC in older adults demonstrated that the representational distinctiveness of experimentally familiar faces, but not personally familiar faces, was preserved across the lifespan. In contrast to young adults, a representationally distinct code for personally familiar faces was revealed only in the posterior superior temporal sulcus (pSTS) of older adults, which is a key node in the core face processing system. Comparing across regions of interest also revealed that pSTS was representationally distinct from both the extended system and other structures comprising the core system. Lastly, we found that activity patterns in the fusiform face area and occipital face area of young adults predicted response times on a behavioral oddball task in which personally familiar and novel faces were pitted against one another.